1. Field of the Invention
The invention relates generally to wireless communication and more particularly to systems and methods for multi-mode wireless communication.
2. Background
The wireless communication spectrum is becoming increasingly crowded. Specifically, more and more communication users and more and more communication types are utilizing the limited frequency spectrum that is available. Reception of wireless communication becomes increasingly difficult as more users and types of communications increasingly consume the available communications spectra.
Some communication types occupy overlapping frequency bands. For example, wireless local area networks (WLAN) and wireless personal area networks (WPAN) sometimes occupy the same frequency and space. For example, the communication standards known as 802.11b and g (hereinafter collectively, “802.11”) operate at approximately 2.4 gigahertz (GHz), while the communication standard known as Bluetooth also operates at approximately 2.4 GHz. See IEEE Std 802.11b, IEEE Std 802.11g and IEEE Std 802.15 (hereinafter, “Bluetooth”), all published by The Institute of Electrical and Electronics Engineers, Inc., New York, N.Y., 1999 (Reaff 2003). It is commonly very difficult if not impossible for wireless communication receivers to differentiate between 802.11 and Bluetooth communications.
It would be convenient to allow Bluetooth and 802.11 systems to operate within the same physical location. But the 802.11 and Bluetooth communications interfere with each other, making it nearly impossible to receive either the 802.11 communication or the Bluetooth communication or both while communication of both types are being transmitted in close proximity. A possible solution is to turn off the 802.11 communications in certain time periods, to allow for Bluetooth communication to proceed without interference during those time periods. However, this approach would decrease the communication capacity of the 802.11 communication and the Bluetooth communication.
Typically, for a wireless communication device to receive wireless communication signals in multiple bands (or frequencies) the device must have multiple receiver architectures. That is, for example, the device typically must have two low noise amplifiers (LNA's) and two radio frequency (RF) filters in order to receive signals in two bands. For example, a wireless communication device may be able to receive signals in both the U.S. cellular band between approximately 824 MHz and 894 MHz, and the U.S. personal communication service (PCS) band between approximately 1910 MHz and 1990 MHz . Such a device would have a cellular LNA and a separate PCS LNA in addition to a cellular RF filter and a separate PCS RF filter. The LNA's and RF filters are narrowband devices. This means that they work especially well at their designated signal frequency, but that they do not work well at other frequencies or that they reject signals at other frequencies. Additionally, typical multi-band receivers operate by receiving and processing signals in one band at a time. For example, typical mobile telephones in the United States can only receive data in either the cellular band or the PCS band at any given time. These devices cannot operate in the cellular band and the PCS band simultaneously.
Another part that may be duplicated in some multi-band receivers is the antenna. Some receivers require multiple antennas to receive multiple bands. Indeed, some receivers require multiple antennas even to receive signals from multiple sources in the same band.